Method for making paper



J. D. HILL ET AL METHOD FOR MAKING PAPER Oct. 1G, 1956 2 Sheetss-SheeL 1 Filed July 25, i952 'Oct 16 19.56 J. D. HILL ET AL. 2,767,091

METHOD Foa MAKING PAPER Filed Juiy 25, 1952 v 2 sheets-snee: 2

MMI @s yThis .invention relates to a novel method forproducing ia. fibrous composition, such as =paper, which contains a thermoplastic or waterproofing` material, such as bitumen or o ther heat fusible substances.

The addition of a heat fusible substance, suchas'bitumen or. asphalt, during the paper making process vhas been heretofore. employed in many different lways with varying degrees of success. Indeed, the multiplicity of methodsprroposed is, of itself, indicative of lthe many problems existing in the handling of a heat fusible substance in the. conventional paper making machinery'fand ofthe dissatisfaction with the results of the previousapproaches to these problems.

` In` order .to produce a ,sheet of paper of considerable stiffness and strength with sufficient Vmoisture resisting vqualities, it is generally accepted that a relatively large amount 'of bitumen, or other heat fusible, water-repellent substance, must' be added to the ordinary paper stock. Therpresence of the` bitumen in the stock offers a serious problem in being able `to adequately control theA bitumen lso'that it'does not adhere to thepaper machine' and thereby interfere with the normal operation 4of themachine.

Moreoven` inthegforming `of a multi-ply paperboard, having atl least one inner sheet, containing Y aV heatfusible substance, such asrbitumenL-there hasheretoforeAbe'en considerable difiiculty in making Aa strong, moistureresistantV boardwithout having., the bitumen penetrate --fthe outer sheets or liners. The*penetration` of the 'liners by thfbitumennot'ronly mars the appearance .of the Ifir'iis'hed producgbut also presents other deficiencieswhich detractfrom the usefulness oflthe product. T he,presence vofan appreciable amount of bitumen, orother Vheatfusible substance, on the outer surface of the liners notionly permeates the surrounding atmosphere with the odor of vthesubstancebut also presents thedanger of contaminating'food materials and the like whichmightbe contacted bythe liners. Furthermore, thestriking .through ofthe ,'biturn'en', wwith respect to the liners,-. naturally resultsin a ,decrease in jthe amount 'ofbitumen bonded` between-the linersand', therefore, reduces the strength, .'stifness, and moisture-'resistant properties of the paper` board.

'1 Accordingly, itis'the principal object ofthe .present .invention to 'provide an improved methodwfor .the'fhan- Y dling of a thermoplastic, water-proofing material during the making 'of paper, which will leliminate-,or minimizethediiiiculties `discussed above, and thereby produce a jpaper board vC )f- Vimproved strength, lregulated sty-iffness,nd moisture-proof. qualities.

Anothengobjecb-of -this invention is to provide. a methgod 4for-uniformly .dispersing comminuted;particlesfof a thermoplastic, water-proofing material, throughout a mass uofybrous pulp, and maintaining the vuniformity ofthe mixture'during the y entire papera making process Vwith a rninimum" 'of' particle -lossin the process.

.gAfffurtherxobject of. the present invention is to prio- .vidennovel-.and improved apparatus for the lhandling'of atherrnoplastic, water-proofing material in the manufacture ,of paper.

-Theseand other objects and advantages of the invention will be made more apparent by reference to lthe following description and the accompanying drawing, wherein:

Fig. ll is a diagrammatic showing of apparatus which may be used,in making paper in accordance with the present invention.

Fig.'2. is' an enlarged sectional view of a portion of theapparatus in Fig. 1.

Fig. 3y isV a fragmentaryperspective View of a fourply paperboard made .in accordance with the present invention.

According to the invention, a thermoplasticrmaterial, such as a lharfd, dry and friable bitumen, is finely divided .and `added tothe fibrous. pulp as lthe latter is being cir- .culatedfin` a water solution in the beater. The fine particles ofthe bitumen remain in suspension in the beater andarenrixed uniformly throughout the fibrous pulp. Thelmixturein thebeater is then further refined in a Jordan, or similar machine, from which it isfed to a papermaking machine of the type having a foraminous,

' web-forming( surface.

'tice,' to avoid adherence of the bituminous kparticles to 'the machine. The remainder of the ltreatment of the bitumen and pulp mixture generally follows conventional paper making practices.

"-"Referring to Fig. 1, there is illustrated one embodi ment of the invention, wherein the apparatus is indicated diagrarnmatically, involving the production of a 4'multiply paper board. Whereas vthe invention will be Vdescribed with respect to a process involving the use of a bitumen and in connectionwith cylinder machines, it will be readily apparent as the disclosure progresses that certain of the novel principles set forth herein may be equallyapplicable toother paper making processes and other .Web-formingequipmentand other thermoplastic materials.

Inithe making of a four-ply paper board, there is pro- 'vided a. breaker-beater l() for treatment of the wastepap'er, -or other stock', to be used in producing a fibrous .pulp-.fori theA main beater 12 in which the` bitumen and pulp are to be mixed priorto forming the paper board. .Any suitable means, such as a conduit 14Hand a pump `16, may be provided 'for transferring the pulp from the rbreaker-beater. to the main beater 12.A

A.The main beater-w12 is generally Vof conventional construction, including a beater roll'lS, with a slight' adaptation to accommodate structure for introducing the bitu- .men intolthe beater. Preferably at one end of the beater -12, .there is provided a cover 2t) which includes a pair 4of adjacent openings 19 and 2l for the introduction of 604 .airfrom'the covered portion of the beater, respectively.

bitumen into theA beater and for the escape of pressure 4For handling. the bitumen prior to its additionv to the pulp in' the main beater l2, there is provided a storage bin-22 having'v means associated'therewith, such as a fscrew-,typeconveyor 24, for conveying the bitumen to a pulverizing mechanism generally designated by the nurn- `ber26.

v,The `pulverizingv mechanisrnf26 (Fig. l2) comprises a `pairiof ,conventional grinders Orhammer mills 2S and' 3 cylindrical housing 29 having a top cover 31, and suitable inwardly extending horizontal flange members 33 for supporting the grinder. Suitable bearing means (not shown) are provided in the housing 29 for supporting the center shaft 35 t'o which is attached a series of radially spaced hammers 36 which grind the material against a breaker bar 37 disposed in the path of movement of the hammers.

The upper portion of the chamber for the grinder 28 also includes a top and side wall forming portion 39 which supports `an adjustable gate as well as supporting the lower end of `a pipe 38 which extends upwardly through the top cover 31. The pipe 38 affords means for the introduction of a cooling medium, such as compressed air, into the grinders and includes at its outer end a removable cover 40. The adjustable gate 41 is arranged to control the flow of material into the upper grinder chamber.

The lower portion of the grinder 28 comprises a foraminous metal plate or screen 32 which serves 'as a grading medium for the pulverized material. Metal plates having holes approximately 1%;4 in diameter boredY therein, in as closely spaced relation as possible, have been used fo-r this screen, but it is to be understood that Ia standard metal screen of approximately 30 to 40 mesh may also be used.

The lower grinder 30 also includes a cylindrical housing 41 which is disposed in vertical alignment with the housing 29 of the upper grinder and is separated therefrom by a short cylindrical section 43 suitably secured between the two housings 29 and 39. The lower grinder is generally similar to the upper grinder 28, having a center shaft 35', a series of hammers 36 and a breaker bar 37', and is suitably supported in its housing by a pair of plate members 45 which are secured to an upper portion of the housing 41. The grinder 30 also includes a foraminous metal plate 34 at its lower portion which is similar to plate 32. A suitable source of power, such as ,an electric motor (not shown), is drivingly connected to ythe center shafts 3S and 35 of the grinders.

Thus it is seen that the bitumen enters the upper grinder chamber, where it is pulverized, and passes downwardly through the screen 32 to the lower grinder 30 where it is further ground. Finally the pulverized particles of bitumen pass ythrough the screen 34 :and opening 19 into the main beater 12 where the fibrous pulp is being mixed.

As the finely divided particles fall from the grinders into the beater 12, there is a considerable amount of dust v formed in the surrounding .air which must be controlled in order to avoid loss of the asphalt and, also, to prevent injury to persons working in the area. The purpose of the cover 20 and the opening 21, which is disposed in close relation to the opening 19 through which the bitumen particles fall, is to assist in controlling this dust.

A vertically extending stack or pipe 44 is positioned over the opening 21 in the cover 20 in comunication with the atmosphere, and includes a plurality of shower heads 47 through which water is directed downwardly to settle the dust tending to rise from the beater during the fall of the bitumen particles. It has been found that hot water is most effective in this dust settling operation and, consequently, water having a temperature below the softening point of the bitumen may be satisfactorily used. It should also be noted that the operation of the shower heads 47 is `designed to avoid interference with the effectiveness of the pipe 44 as a relief for the air pressure created in the covered portion of the beater during the operation of the grinders and the fall of the bitumen.

After the fibrous pulp and the particles of bitumen have been thoroughly mixed in the main beater 12, the mixture is pumped or otherwise conveyed through a conduit 46 to a Jordan 48, or a similar machine, for further mixing and refining. From the Jordan lthe pulp mixture 1s conveyed to the paper making machine in any suitabl@ way. As shown, the mixture is first pumped to a stock chest 50 and then flows, by gravity or otherwise, to the web-forming equipment which in the present instance comprises two cylinders 52 and 54, respectively, which are used in forming the inner layers of the four-ply board. The flow to the vats of the cylinders 52 and 54 may be controlled by any of the well known means, such as a gate valve controlled by a spoon (not shown) in the conduit between the stock chest and the vats.

A separate beater 56 supplies pulp to a second stock chest 58 in the conventional manner to feed the vats for the outer cylinders 60 and 62 which form the non-bitumi nous outer sheets or liners.

The cylinders 52 and 54, respectively, which form a web from the bitumen-pulp mixture, are conventional except as to the size of the openings in the foraminous cylindrical surface thereof. In lieu of the conventional 50 mesh screen, or larger, on the surface of these cylinders, there is provided a screen of finer mesh in order to avoid loss of the finely divided asphalt particles in the white water. With the described apparatus it has been found desirable to use either a 70 or 80 mesh screen.

Although asphalt does not usually become sticky at temperatures lower than about F. it has been discovered that for some reason not yet known it is very helpful in the prevention of adherence of the bitumen particles to the cylinders and other parts of the machinery to maintain the water in the cylinder at a temperature below 70 F., preferably around 50 F. Then too, it is desirable for most efficient operation in the process to use fresh water in the cylinder vat's and new felts at the wet end of the paper making machine at the beginning of each run of paper stock.

The paper making operation following the formation of the webs on the cylinders involves standard practices with the usual presses and dryers. The temperature of the drying rolls varies from about 220 at the wet end to about 316 a-t the dry end, and the speed of the paper in this process is related to the temperature and number of drying rolls.

It will be apparent from the foregoing, that the process and apparatus involved is not limited to the making of multi-ply paper. In fact, the procedure has been successfully followed in the making of liners for corrugated boxes, wherein added strength, stiffness and moistureresistant qualities are important. The above described features which afford advantages in the process, prior to and including the forming of the web on the cylinder, are obviously equally effective without the addition of other sheets or webs to form a multi-ply paper board, as in the described instance.

Example With the foregoing apparatus and method there may be produced a very strong, stiff and moisture-proof paper board by using a hard, dry and friable asphalt having 0 penetration at 77 F. (ASTM D5-25 at 77 F. 100 grams, 5 seconds) and a melting point of between 220 F. and 230 F. (ASTM D3-26). The asphalt is conveyed from the bin 10 to the pulverizing mechanism 26 at a uniform rate of delivery commensurate with the capacity of the grinders which operate at a full load speed of 2400 R. P. M., with screens 32 and 34 having M34" diameter openings.

It might be noted at this point that the grinders should not be operated at a speed suflicient to elevate the temperature in the grinders to the melting point of the asphalt. Also, in using the described asphalt and 8O mesh screen on the cylinders 52 and 54, the screens 32 and 34 in the grinders should be of about 30 to 40 mesh, that is having openings of about %4 diameter, to obtain the best results. A larger opening in the screens produces particles of sufficient magnitude to strike through the liner of a four-ply paper board under the heat of the dryer 17011S A .much Smaller opening in the screens re- Lquires longer operationjoflhthe,V grindersV withoutgfany "appreciable" 'improvement in' the V,quality of the paper board.

With the grinders operating as' described, thereis norjmallyno need for. cooling the` inside ofthep'pulverizing "mechanism housing. However, .ithas' been found that under vconditions of high .temperatures outside'mof 'the fgrinderhousing, `it may be desirableto cool'the`.inside j' of thehousing by'the` introduction "oflcompressed air throughthe pipe 38 at the, top ofjthenp'pper mill'28.

Prior to operation'of 'the conveyor'24 and pulverizing mechanism 26, a waste papenstockis mixed in the breaker-beater` vandfthenfed tuthemainV beater 12 until the lattervis about -halffull. VThis waste paper stock consistsrrnainly ,OLmatGIaIf-frpm old corrugated r fboxesandwaste from4 new` boxes, neither of which contain bitumen oranyv similar substance.

4While-thebeater roll 18Vis`down and operating to circulatetheywaste papervstock, the asphalt is conveyed from fgthe bin 22,throughthe pulverizllg'mechanisnnand into Athe beater 12 until., Vthe amount of material therein `includes y66% ystockand 40% asphalt, by dryweight. Specifically, for 1`200fflbs. YVof dry rstock there is;;added 1,0 005jl bs.v of asphalt.

- i During the v falling of, the, asphalt fparticles from the i lowerjgri-nder 30 into,t he ,main beaten 12, a fine; spray of-hot water is directed downjthepipegti to prevent `loss 10E'asphaltyparticles throughgthisfalr-vent. The water is t preferably kept at va i temperature i of. "1902200 ,in' order `to be most effective Vas asdust settling'means, without-causing any objectionable softening of the asphalt particles.

The beater 12 Withlthe'asphalt and-.Waste paper stock `mixturevis :then operated forfaboutihalfsan hourinforder Vto 'disperse'the asphalt particles uniformly throughout the stock where they will remain'jinesuspension. Also, once the asphalt particles are in thebeater, asmall ,amount f of paper=makers alumjzrnay be "addedjto precipitate Q.any

Y --unattached asphalt ontoithebers. '@Withthe, beater'containing 2200 lbs. of dry stock andasphaltandA 2800` gallons of water, 66 lbs. of alum are added to the mixture in the beater. Thus the added alum constitutes about 3% of the dry weight of the pulp and asphalt. The mixture in the beater i2 is then pumped through the conduit 46 to the Jordan 48 for further mixing and grinding action, and then to the stock chest 50.

Meanwhile, the stock for the liners is prepared in the second beater 56 and delivered to the second stock chest 58. The stock from the two chests is then metered, in the usual way through gate valves controlled by spoons, through separate conduits to the four cylinder vats. The vats for the cylinders 52 and 54 receive stock from the chest 50 containing the asphalt mixture, and the vats for the cylinders 60 and 62 receive stock from the chest 53 containing the liner stock.

As noted previously, the foraminous surface of the two cylinders 52 and 54, which form sheets 64 and 66, respectively, from the asphalt-containing Stock, comprised an 8() mesh screen, as opposed to the ordinary 30-50 mesh screen commonly used on the cylinders in paper machines. The provision of a finer meshv screen is important in keeping the finely divided particles of asphalt from filtering through the cylinder and escaping in the wash water in the cylinder, which action would disturb the uniformity of the mixture as well as diminish the amount of bitumen in the paper formed.

The sheets or webs formed on the cylinders are picked up on the wet felts from which they travel through the usual rolls to the press rolls and dryers. T he sheets from the four cylinders are formed, in the course of their travel, into a single sheet 63 of four-ply paper board with the uniformly dispersed bitumen in the inner two sheets 64 and do being fused by the heat of the dryer rolls to unite the four sheets which are further bonded together by the compressing action of the calender stacks.

The result of the foregoing process is an improved imliltiplygraner board hai/ins ddd Strensthaild mpraiieii moisture-resistant properties over previously'known` similar products. It is believedth'atthe ,ability yto uniformly disperse very. fine particles'of asphalt `throughoutthe 'fibrous Ypulpvand Ymaintainthese particles in such relationl of; the machinery.

LMoreover, by controlling the uniformity` of the mixture ".Of pulp andjasphalt, particles,.and the relative quantities 15 Y thereof,` throughout the en tire paper making process, it is possible to closely regulatethe stiffness of thelresulting 'paper board. Particularly inthermanufacture. of boxes the dry stiffness quality Aof the paper board is important and, consequentlyitlis a definiteadvantage to be able to control the s tiifness asis possible in thedisclosed process.

It `should be understood that, although theinvention has been: particularly described with respect to its applilcation" to aideiinite proportion of materials and a particular4 type of thermoplastic binder and paper stock, other Vtypes of "thermoplastic binders and paper stocks .and relative proportions thereof Vmay'be effectively used .without deviating from `the invention. The percentage of binder Y materialis; of course, dependent upon the results desired;

Furthermore, wherev asphalt has been used in the described processit has been found that an asphalt having a melting *point as `low as V190" is' satisfactory. Accordingly, it

should be noted that the describedl example Aisnot intended =as alimitation on the scopejof` this invention.

4We claim: i

1 *A .PtCeSS for prediking pareri from .a '@mixtre whichy contains bituminous material and paper-making fflbensaid process 'comprising the comminutiou of dry V bi- "Ytuminous."m'aterial` into air-borne discrete particles all vfeapable ofpassing a screen not coarser than 30 mesh, While maintaining the temperature of the comminuting zone low enough to prevent fusing and coalescing of the individual particles, passing the air-borne particles directly into a beater containing an aqueous paper-making fiber suspension, said particles being in an amount suliicient to impart a substantial waterproofing property to a sheet of paper made from said mixture, mixing the bituminous particles and fiber to achieve a uniform distribution of the bituminous particles throughout the mixture, and forming a sheet from said mixture on a screen while maintaining the temperature of the sheet-forming zone suiciently low to prevent fusing and coalescing of the bituminous particles, whereby substantially all of the bituminous material introduced into the beater will be retained in the sheet in the form of uniformly dispersed and discrete particles.

2. A process for making multi-ply paper wherein at least three fibrous webs 'are formed, respectively, on separate web-forming machines and combined in superposed relation to form a single sheet of paper, at least one inner web being formed from a paper making furnish including bituminous material in an amount suiiicient to impart a substantial waterproofing property to the sheet, said process comprising the formation of said inner web bycomminuting the dry bituminous material into air-borne discrete particles capable of passing a screen not coarser than 3() mesh While maintaining the temperature of the comminuting zone low enough to prevent fusing and coalescing of the individual particles, passing the airborne particles directly into a beater containing an aqueous papermaking fiber suspension, mixing the biturninous particles and fiber to achieve a uniform distribution of the bituminous particles through the mixture, forming a web from said mixture on a screen while maintaining the temperature of the sheet-forming zone sufciently low to prevent fusing and coalescing of the bituminous particles, -forming at least two additional webs from an aqueous paper-making fiber suspension substantially free of any signicant quantity of bituminous material and placing such webs on opposite sides of said inner web, and drying the multi-ply sheet formed from the superposed webs at a temperature high enough to fuse the bituminous particles.

3. A process for producing paper from a mixture which contains bituminous material and paper-making fiber, said process comprising the comminution of dry bituminous material into air-borne discrete particles all capable of passing a screen not coarser than 30 mesh, while maintaining the temperature of the comminuting zone low enough to prevent fusing and coalescing of the individual particles, passing the air-borne particles directly into a beater containing an aqueous paper-making ber suspension, said particles being in an amount suicient to impart a substantial waterproofing property to a sheet of paper made from said mixture, mixing the bituminous particles and ber to achieve a uniform distribution of the bituminous particles throughout the mixture, and forming a 'sheet from said mixture on a screen having openings not -coarser than 70 mesh, while maintaining the temperature of the sheet form-ing zone at a temperature not greater than 70 F. to prevent fusing and coalescing of the bituminous particles, whereby substantially all of the bituminous material introduced into the beater will be retained in the sheet in the form of uniformly dispersed and discrete particles.

4. A process for producing paper from a mixture which contains a bituminous material and paper-making liber, said process comprising the comminution of dry bituminous material having a melting point labove 190 F. into air-borne discrete particles all capable of passing a screen not -coarser than 30 mesh, While maintaining the temperature of the comminuting zone low enough to prevent fusing and coalescing of the individual particles, passing the air-borne particles directly into a beater containing an `aqueous paper-making ber suspension, said bituminous .material comprising about 40 percent, by dry weight,

References Cited in the le of this patent UNITED STATES PATENTS Re, 15,461 Perry Sept. 26, 1922 253,655 Allen Feb. 14, 1882 756,214 Cornell Apr. 5, 1904 785,025 Sherwood Mar. 14, 1905 1,515,821 Avery Nov. 18, 1924 1,621,888 Kirschbraun Mar. 22, 1927 1,694,523 White Dec. 11, 1928 1,904,087 Schacht Apr. 18, 1933 2,022,311 Fisher Nov. 26, 1935 2,162,687 Fischer lune 13, 1939 2,387,429 Cate oct. 23, 1945 2,400,544 Kline May 21, 1946 2,493,507 Sutherland Jan. 30, 1950 2,534,703 Fenelon et al, Dec. 19, 1950 2,538,926 Sutherland Jan. 23, 1951 2,602,029 Bradshaw July 1, 1952 FOREIGN PATENTS 116,040 Great Britain May 30, 1918 OTHER REFERENCES Pulp and Paper, by Casey, vol. I, pages 435 and 460, published by Interscience Publishers, Inc., New York (1952). (Copy in Div. 67.) 

1. A PROCESS FOR PRODUCING PAPER FROM A MIXTURE WHICH CONTAINS BITUMINOUS MATERIAL AND PAPER-MAKING FIBER, SAID PROCESS COMPRISING TE COMMUNICATION OF DRY BITUMINOUS MATERIAL INTO AIR-BORNE DISCRETE PARTICLES ALL CAPABLE OF PASSING A SCREEN NOT COARSER THAN 30 MESH, WHILE MAINTAINING THE TEMPERATURE OF THE COMMINUTING ZONE LOW ENOUGH TO PREVENT FUSING AND COALESCING OF THE INDIVIDUAL PARTICLES, PASSING THE AIR-BORNE PARTICLES DIRECTLY INTO A BEATER CONTAINING AN AQUEOUS PAPER-MAKING FIBER SUSPENSION, SAID PARTICLES BEING IN AN AMOUNT SUFFICIENT OF IMPART A SUBSTANTIAL WATERPROOFING PROPERTY TO A SHEET OF PAPER MADE FROM A MIXTURE, MIXING THE BITUMINOUS 